Costs to run an open access journal

I've talked to a few people recently who were curious about how a journal like JCGT can be totally free to submit and to read, and how that model is sustainable. Here's a rundown of the parts of running JCGT and what they cost:

Principal Staff (Editor in Chief, Managing Editor, Advisory board)	volunteer	$0
Editorial Board	volunteer	$0
External Reviewers	volunteer	$0
Copyediting	volunteer by Managing Editor and (occasionally) EIC	$0
Review management	email, google spreadsheets, google drive	$0
Web site design and scripting	Custom static html/javascript created by advisory board member/former EIC Morgan McGuire and maintained by current EIC Marc Olano	$0
Domain registration & email	(Bluehost) cost paid informally by staff	~$25/year
Hosting, DNS, CDN	(Amazon) cost paid informally by staff	~$75/year

Pretty much all journals, open access or not, have a volunteer editor in chief, volunteer associate editors, and volunteer reviewers, so JCGT is not unusual in that regard.

At least in computer science, it's common for journals to not have any formal copyediting. Papers are formatted according to a template and final "camera-ready" version is produced by the authors. JCGT is unusual in performing an explicit copyediting step, though I believe it improves the quality and consistency of the papers we publish.

Review management software is definitely one place where we do skimp. There are free alternatives, but so far with our submission rate averaging about 30 papers per year, the manual version has worked well enough.

Hosting related costs are the one thing we can't get entirely for free. The costs of about $100/year are paid out of pocket by some of the journal staff as a service to the community. Paraphrasing one of my colleagues, for less than the cost of a single traditional journal subscription, the whole community benefits.